Hybrid regulators have several advantages compared to buck regulators and Switched-Capacitor (SC) regulators. Hybrid regulators can be more efficient and can use smaller inductors than buck regulators. Hybrid regulators can efficiently regulate across a wider range of input to output voltage ratios. In contrast, SC regulator efficiency is high at N:M input to output voltage ratios (where N, M are integers), but efficiency drops as the ratio deviates from N:M to non-integer ratios.
Hybrid regulators can operate with multiple operating modes to support a wide range of input to output voltage ratios. For example, in a H21 mode, a hybrid regulator can support an input to output (VIN:VOUT) ratio between 2:1 and 1:1. As another example, in a H32 mode, a hybrid regulator can support a VIN:VOUT ratio between 3:1 and 2:1. FIGS. 1A-1C show an example of a single hybrid regulator operating in a H32 mode and FIGS. 2A-2C show an example of a single hybrid regulator operating in a H21 mode. In FIGS. 1A-1C, the VIN:VOUT ratio can be between 2:1 and 3:1. In FIGS. 2A-2C, the VIN:VOUT ratio can be between 1:1 and 2:1. The hybrid regulator in FIGS. 1A-1C and 2A-2C can switch between these two modes (i.e., the H32 mode and the H21 mode) by changing which switches are turned on and off.
The upside of having multiple operating modes is that it enables a single regulator to support a wide range of VIN:VOUT ratios, which can help cover a wide range of end applications with a single product. There are two downsides of having multiple modes. First, the regulator can require an additional feedback control that determines which mode to operate in. Second, there can be glitches while transitioning from one mode to another that can cause malfunction of the regulator. Different modes require different switches to turn on/off. If the timing of the switch activity is misaligned, some voltages on certain switches could be wrong, and a high voltage applied to a switch could break it. If surrounding conditions, such as input voltage or output current, change quickly, the regulator might need to change modes quickly, which can require very fast feedback control to change modes quickly (which feedback control can be challenging to design) and/or cause glitches during quick mode transition if all the timing requirements of related signals are not properly aligned (which proper alignment can be challenging to guarantee). For example, a hybrid regulator might be operating at 1.8V input and 1V output in H21 mode, and due to a system requirement, the input might need to quickly change to 2.5V, at which time the regulator needs to quickly change to H32 mode.
Accordingly, it is desirable to support a wider range of VIN:VOUT ratios with as few modes as possible.